Delay management for distributed communications networks

ABSTRACT

A method for programming the delay for a node in a communication system is disclosed. The node receives a selected delay value and a signal path delay value indicating a delay for signals communicated to the node. The signal path delay comprises an aggregation of transport delays calculated by each node for segments of the communication system between the node and a host node. The method further calculates an additional delay necessary to meet the selected delay value.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/839,086filed on Aug. 15, 2007 and entitled “DELAY MANAGEMENT FOR DISTRIBUTEDCOMMUNICATIONS NETWORKS” (currently pending), which is incorporatedherein in its entirety by reference.

BACKGROUND

Distributed antenna systems are widely used to seamlessly extendcoverage for wireless communication signals to locations that are notadequately served by conventional base stations or to distributecapacity from centralized radio suites. These systems typically includea host unit and a plurality of remote units. The host unit is typicallycoupled between a base station or radio suite and the plurality ofremote units in one of many possible network configurations, e.g., huband spoke, daisy-chain, or branch-and-tree. Each of the plurality ofremote units includes one or more antennas that send and receivewireless signals on behalf of the base station or radio suites.

One common issue in distributed antenna systems is adjusting for thedifferent delay associated with each of the remote units. Each remoteunit is typically located at a different distance from the host unit. Toallow the various antennas to be synchronized, a delay value istypically set at each remote unit. Unfortunately, conventionaltechniques used to establish the delay for the various remote units haveadded significant complexity and/or cost to the distributed antennasystem. For example, some common network synchronization techniquesinvolve the use of various locating technologies (e.g., globalpositioning systems, or GPS) that add further complexities and cost tooperating these distributed antenna systems reliably and efficiently.

For the reasons stated above and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art forimprovements in delay management for distributed communicationsnetworks.

SUMMARY

In one embodiment, a method for managing delay between nodes in anetwork having a plurality of nodes coupled together by a plurality oflinks is provided. The method comprises discovering a transport delayvalue for each of the plurality of links. At a first one of theplurality of nodes, the method generates a signal path delay value foreach of the plurality of nodes coupled to the first one of the pluralityof nodes using the discovered transport delay value associated with alink of the plurality of links that couples that node to the first oneof the plurality of nodes and passes the generated signal path delayvalues over the links to the nodes of the plurality of nodes coupled tothe first one of the plurality of nodes. At each additional node of theplurality of nodes, the method stores a received signal path delay valuefor the additional node to enable management of the delay for theadditional node, generates a signal path delay value for each adjacentnode of the plurality of nodes coupled to the additional node using thereceived signal path delay value and the discovered transport delayvalue for the link between the additional node and the adjacent node,and passes the generated signal path delay values over the additionallinks to the adjacent nodes.

DRAWINGS

These and other features, aspects, and advantages are better understoodwith regard to the following description, appended claims, andaccompanying drawings where:

FIG. 1 is a block diagram of a distributed communications network;

FIG. 2 is a block diagram of an application framework for a distributedcommunications network;

FIGS. 3 and 3A are block diagrams of a data packet in an applicationframework for a distributed communications network; and

FIG. 4 is a flow diagram illustrating a method for delay management in adistributed communications network.

DETAILED DESCRIPTION

The following detailed description relates to delay management fordistributed communications networks, e.g., a distributed antenna system.The delay management discussed here enables a network manager toestablish a desired delay at a plurality of nodes in apoint-to-multipoint communications network with a suitably high degreeof repeatability and control. The desired delay can be for each of thenodes collectively or for each individual node. Advantageously, thecommunications network discussed here uses a distributed approach todetermine a signal path delay from a host to each node in the system.This is accomplished at each node by discovering a transport delay(e.g., the travel time) over the link between the node and its adjacent(e.g., successive) nodes in the network. For example, each of the nodeslearns the distance between itself and any downstream, adjacent nodes.Based on these transport delays between nodes, the nodes in the systemcooperate to determine the signal path delay for each remote noderelative to the host node. Furthermore, in determining the signal pathdelay, each node also accounts for individual internal processing delaysof the nodes. Once the signal path delays are determined, the desireddelay at each remote node can be definitively established by accountingfor the signal path delay back to the host node and any known internalprocessing delays.

In one implementation, the delay management discussed here incorporatesthe use of a delay monitor channel and a delay management channel in adata frame. The delay monitor and delay management channels are used tocommunicate data between nodes to establish a common time base for thenetwork without using excessive overhead. To establish the common timebase, the nodes determine the transport delay between nodes using thedelay monitor channel as described in more detail below. The nodesfurther transmit data, e.g., the signal path delay values, in the delaymanagement channel to their adjacent nodes. Each node further combinesthe transport delay to a succeeding node determined using the delaymonitor channel with a signal path delay received over the delaymanagement channel and a respective internal processing delay. Thisvalue is in turn passed over the delay management channel to theadjacent node as a signal path delay for that node. The plurality ofnodes thus propagates the accumulated delay to successive nodes untilall terminating nodes in the network have received a signal path delayback to the host node. In this manner, every remote node in the systemis constantly aware of its distance (in signal time) from the host node.This allows each remote node to independently adjust the delay of itstransmissions to maintain a selected delay in the system at each of thenodes.

Furthermore, the delay management discussed here does not require theuse of additional node positioning and timing techniques (e.g., usingGPS) to synchronize message delivery between the nodes. Rather than relyon a separate system (e.g., GPS timing references) to determine thetiming delay between each of the nodes, the delay monitor and managementchannels provide a substantially simplified means of determining signalpath delays between each of the nodes.

The delay management technique described herein is topology independent.The delay management technique is applicable to a wide range of networktopologies, e.g., star, tree and a daisy-chain network configuration(and combinations thereof). Moreover, this delay management ismedium-independent, and functions on a plurality of networkinfrastructures, such as wireless, free space optics, millimeter wave,twisted pair, coaxial, optical fiber, hybrid fiber, and suitablecombinations thereof.

FIG. 1 is a block diagram of an embodiment of a communications network100. The communications network 100 represents a point-to-multipointcommunications network that comprises a data source 101, a host node 102responsive to the data source 101, and remote nodes 104 ₁ to 104 _(M) incommunication with the host node 102. The host node 102 comprises a hostdigital interface 103 and a host transport interface 105 responsive to ahost node processor 106. Each of the remote nodes 104 ₁ to 104 _(M)comprises a remote transport interface 107 ₁ to 107 _(M) and an RF todigital interface 109 ₁ to 109 _(M) responsive to a remote nodeprocessor 108 ₁ to 108 _(M). Each of the RF to digital interfaces 109 ₁to 109 _(M) is further responsive to antenna ports 110 ₁ to 110 _(M),respectively. In one implementation, the host node processor 106 andeach of the remote node processors 108 ₁ to 108 _(M) comprise at leastone of a microcontroller, an application-specific integrated circuit(ASIC), a field-programmable gate array (FPGA), a field-programmableobject array (FPOA), or a programmable logic device (PLD). It isunderstood that the network 100 is capable of accommodating anyappropriate number of remote nodes 104 ₁ to 104 _(M) (e.g., at least oneremote node 104 with at least one remote transport interface 107, remotenode processor 108, RF to digital interface 109, and antenna port 110)in a single network 100.

The host node 102 and the remote nodes 104 ₁ to 104 _(M) arecommunicatively coupled by a plurality of signal paths in atree-and-branch network configuration representing a plurality oflevels. In the example embodiment of FIG. 1, the tree-and-branch networkconfiguration further includes signal switches 112 and 114. Each of thesignal paths illustrated in FIG. 1 are at least one of an electricallink, an optical fiber link and a wireless transport link (e.g.,millimeter wave, free space optics, or suitable combinations thereof),providing a medium-independent network architecture. It is understoodthat additional network configurations (e.g., a hub and spoke, a commonbus, and the like) are also contemplated.

The host digital interface 103 and each of the RF to digital interfaces109 include ports D1, D2, and D3. The ports D1, D2, and D3 areconsidered representative of a plurality of signal interface connections(e.g., RF, Ethernet, and the like) for the host digital interface 103and each of the RF to digital interfaces 109. Similarly, the hosttransport interface 105 and each of the remote transport interfaces 107include ports T1, T2, and T3. The ports T1, T2, and T3 are consideredrepresentative of a plurality of transport interface connections for thehost transport interface 105 and each of the remote transport interfaces107. For example, the host transport interface 105 and each of theremote transport interfaces 107 provide an appropriate signal conversion(e.g., at least one of digital to serial and serial to optical fiber)for each of the remote nodes 104 and the host node 102 of the network100. It is understood the ports D1 to D3 and T1 to T3 shown in FIG. 1are not to be considered limiting the number of signal interface andtransport ports contemplated by the system discussed here (e.g., thesystem 100 is capable of accommodating any appropriate number ofinstances of signal interface and transport ports).

Each remote node 104 ₁ to 104 _(M) introduces one or more intrinsicprocessing delays. For example, the remote transport interfaces 107includes a first intrinsic processing delay when passing signals betweenthe transport interface connections T1 and T3 (commonly referred to as a“fiber-to-fiber” delay in this example). Similarly, each of the RF todigital interfaces 109 includes a second intrinsic processing delay forconverting signals between digital and RF. In some instances, theintrinsic processing delays in RF to digital interface 109 areasymmetrical. This means that the intrinsic processing delay forupstream signals (signals going to the host 102) and the intrinsicprocessing delay for downstream signals (signals coming from the host102) are different. In one implementation, the various intrinsicprocessing delays are embedded in each of the remote node processors 108₁ to 108 _(M) for use in establishing the requested delay for the node.

In operation, network 100 implements a distributed process fordetermining the signal path delay for each node in the network 100 backto host node 102. In this distributed process, each node in the network100 discovers individual transport delays to any adjacent nodes (e.g.,any nodes adjacent to the host node 102 or the remote nodes 104 ₁ to 104₁₀ in the downstream direction). Beginning at the host node 102, asignal path delay value based on the transport delay discovered for eachof the adjacent nodes is generated and passed on to the adjacent nodes.For each succeeding level of the adjacent nodes in the network 100 (ifany exist), the remote nodes 104 ₁ to 104 _(M) each aggregate the signalpath delay for that node with the transport delay to the next, adjacentnode and propagate a signal path delay value for the adjacent node tothe adjacent nodes in that level. This process of aggregating thereceived signal path delay with the known transport delay to adjacentnodes and passing on a signal path delay is repeated until all of thenodes in the network 100 have a value for their respective signal pathdelay.

In one embodiment, the transport delay values are discovered using a“ping” message sent to the adjacent remote node 104. The adjacent remotenode 104 returns the message. The transport delay value is based on thetime between sending and receiving back the “ping” from each of theremote nodes 104 (e.g., a round trip time). Based on the round triptime, the individual transport delay between each of the pairs of nodesis determined.

Continuing with the example embodiment of FIG. 1, the internalprocessing delay at each remote node 104 ₁ to 104 _(M) is alsoincorporated into the calculation of the signal path delay. For example,remote node 104 ₁ generates a signal path delay for remote node 104 ₄.This signal path delay includes the signal path delay from host node 102to remote node 104 ₁ as stored in remote node 104 ₁ plus the transportdelay discovered by remote node 104 ₁ between 104 ₁ and 104 ₄. Thissignal path delay also includes the intrinsic processing delay of thetransport interface 107 ₁ of remote node 104 ₁ to transport signals frominterface T1 to interface T3 (e.g., a “fiber-to-fiber” processingdelay).

The remote nodes 104 ₁ to 104 _(M) use the signal path delay calculatedthrough this process to control the overall delay selected for theremote node. For example, a total delay for each remote node isestablished during network installation. Each remote node sets theamount of delay that it introduces into signals based on the signal pathdelay learned using the above-described process. Thus, a common timebase is established for the nodes in network 100.

FIG. 2 is a block diagram of a framework 200 for network applications.The framework 200 comprises multiple layers, discussed below, thatprovide hardware-related service to enable each node of the network 100to function as shown above with respect to FIG. 1 (e.g., the host node102 discovers the plurality of remote nodes 104 over the network 100).The framework 200 comprises an application layer 202, a network layer204, a data link layer 206, and a physical layer 208. Each layer of theframework 200 compartmentalizes key functions required for any node ofthe network 100 to communicate with any other node of the network 100.

The physical layer 208 is communicatively coupled to, and provides lowlevel functional support for the data link layer 206, the network layer204, and the application layer 202. In one implementation, the physicallayer 208 resides on at least one of an optical fiber network and awireless network. The physical layer 208 provides electronic hardwaresupport for sending and receiving data in a plurality of operations fromthe at least one network application hosted by the host node 102. Thedata link layer 206 provides error handling for the physical layer 208,along with flow control and frame synchronization. The data link layer206 further includes a data frame sub-layer 210. The data framesub-layer 210 comprises a plurality of data frames transferred on thephysical layer 208. Additional detail pertaining to the data framesub-layer 210 is further described below with respect to FIG. 3. Thenetwork layer 204 is responsive to at least one programmable processorwithin the network 100 (e.g., the host node processor 106 or at leastone of the remote node processors 108). The network layer 204 providesswitching and routing capabilities within the network 100 fortransmitting data between the nodes within the network 100. Theapplication layer 202 monitors changes in the transport delay valueindependent of signal frame traffic to maintain a common time base forsignal transmission over the network 100. The application layer 202 isresponsive to at least one of a simple network management protocol(SNMP), a common management information protocol (CMIP), a remotemonitoring (RM) protocol, and any network communications protocolstandard suitable for remote monitoring and network management.

FIG. 3 is a block diagram of an embodiment of the data frame sub-layer210 of FIG. 2, represented generally by the sub-layer 300. The sub-layer300 comprises at least one data frame 302 (or optical fiber frame). Theat least one data frame 302 further comprises a delay monitor channel304 and a delay management channel 306. In one embodiment, the delaymanagement channel 306 includes an (optional) framing bit 308 and one ormore data bits to carry the signal path delay value. In one embodiment,the delay management channel includes up to 16 data bits. As shown, thedelay management channel comprises five bits. In some embodiments, morethan the allocated data bits in one frame are needed to transport thesignal path delay value. In these instances, the signal path delay valueis segmented into groups of bits that are transported in sequentialframes of the delay management channel. When the delay is sent on everydata frame 302, the framing bit 308 is optional. In one implementation,a framing bit flag may be used to indicate that the signal path delayvalue was present in the at least one data frame 302. The (optional)framing bit 308 is used to indicate the beginning of the first group ofbits by setting the value of the framing bit 308 to 1. For thesubsequent groups of bits, the framing bit 308 is set to 0. Thus, forexample, a 16-bit signal path delay value is transported over the delaymanagement channel using four frames with the framing bit 308 of thefirst frame set to 1 as depicted in FIG. 3A. For purposes of thisdescription, this use of multiple frames to carry a signal path delayvalue is referred to as a delay management “superframe.”

In operation, the delay monitor channel 304 is used to determine theso-called “transport delay” between adjacent nodes in the network. Afirst node uses the delay monitor channel 304 to “ping” the adjacentremote nodes 104 to send back the “ping.” This is accomplished bysetting the value of the bit in the delay monitor channel 304 to a “1.”When the adjacent node receives this ping, the adjacent node returns theping by setting the delay monitor channel 304 to a “1” in its next frameto the node that initiated the ping. The transport delay value iscalculated based on the round trip time between the “ping” and thereply. In one implementation, there are at least two “ping” bits used inthe delay monitor channel 305: a forward ping bit and a reverse pingbit. For example, when sending a “request” ping, the forward ping bit isused, and when sending a “response” ping, the reverse ping bit is used.Alternatively, the first node sends the “request” ping, and the adjacentnode sends the “response” ping. Moreover, the first node and theadjacent nodes can ping one another for the data bits carrying thesignal path delay value.

As discussed in further detail below, the desired end-to-end transportdelay between the host node 102 and the remote nodes 104 ₁ to 104 _(M)is programmable for each of the remote nodes 104 ₁ to 104 _(M).Moreover, due to the differences in intrinsic processing and signal pathdelays, each of the remote nodes 104 ₁ to 104 _(M) adjust the requestedtotal delay to account for these differences.

Transport Delay Management

Returning to FIG. 1, the delay management for the network 100 discussedhere is modular and behaves substantially similar for at least one of astar, a daisy-chain, and a tree network configuration. Additionally, thenetwork 100 automatically adjusts for any changes in the delay due tothermal effects, and for any switching protection changes due to, forexample, the signal switches 112 and 114. Each of the remote nodes 104 ₁to 104 _(M) learn the delay going back to the host node 102 from thedelay management channel 306. The delay management discussed here isfurther divided into at least two distinct operations: (1) Learning adownstream delay (away from the host node 102) to an opposing end of thenetwork 100; and (2) Propagating an accumulated signal path delaythroughout the network 100.

Learning the Transport Delay

The host node 102 and each level of the remote nodes 104 ₁ to 104 _(M)are aware which of adjacent remote nodes 104 are downstream and whichare upstream. This information is determined in the discovery of theremote nodes 104 as they are introduced into the network 100. In oneembodiment, the nodes use the delay monitor channel to determine thetransport delay for the nodes that are adjacent to the node in thedownstream direction (away from the host node 102).

In one implementation, each signal path is defined as at least one of amaster and a slave signal link, where a downstream signal link for aparticular remote (host) node 104 (102) is defined as the “master”signal link, and an upstream signal link for the same node is defined asthe “slave” signal link. Moreover, all signal paths coupled to the hostnode 102 are designated as master signal links. On each “master” signallink, at least one of the applicable host node or a remote node 104periodically sets the “ping” bit in the delay monitor channel 304. Thenode then receives responses in subsequent data frames 302 sent incorresponding slave signal links. The round trip delay is measured forthe remote node associated with the master link. The transport delay forthe remote node is determined from this round trip delay by at least oneof the following methods.

A first method involves dividing the round trip delay by two. This roundtrip value includes a “turn-around” delay from when the remote nodereceived the “ping” on the master link and when the remote node returnsthe next frame with the bit set in the delay monitor channel on theslave link. This method has a resolution of ±½ frames.

A second method uses inter-node communication to inform the nodecalculating the transport delay as to the value of the “turn-around”delay. In this process, the node calculating the transport delaysubtracts off the “turn-around” delay from the round trip delay prior todividing the round trip delay by two. This method has a resolution of ±1clock cycle.

A third method uses a preconfigured “turn-around” delay. The turn-arounddelay is set to a known value. The turn-around delay is subtracted offas in the second method described above with the same resolution.

Propagation of Signal Path Delay

Once the transport delay value is determined, the nodes of network 100propagate the signal path delay from node to node. For example, hostnode 102 uses the discovered transport delay values for remote nodes 104₁ to 104 ₃ to generate and send signal path delay to the remote nodes104 ₁ to 104 ₃. In turn, each of remote nodes 104 ₁ to 104 ₃ use thereceived signal path delay as a basis, along with the transport delaythey discovered to their respective adjacent nodes, to generate and sendsignal path delay information to their adjacent nodes. In this manner,the signal path delay values are propagated through the network 100.

Setting the Delay Values

As discussed above, setting the desired end-to-end transport delay willaccount for differences in intrinsic processing delay and thedifferences in signal path delays in the remote nodes 104 ₁ to 104 _(M).In at least one implementation, the desired end-to-end transport delayis fixed. The remote node processor 108 in each of the remote nodes 104receives a request to set the fixed delay value (e.g., from an SNMPagent present in the application layer 202) at each of the antenna ports110 to a specified value. The SNMP agent in the application layer 202subtracts off any known intrinsic processing delays as well as thesignal path delay back to the host unit 102 that has been learned asdescribed above. It is noted that in some embodiments, the intrinsicprocessing delays may vary for both downstream and upstream signals(also known as forward and reverse paths, respectively). As shown below,Equations 1 and 2 illustrate the calculation of the delay that isimplemented, e.g., in a FIFO at the remote node, for the forward andreverse paths at the remote node:DELAY_(FWD)=(Delay_(Requested))−(Delay_(signal-path))−(Delay_(Intrinsic-SD))−(Delay_(Forward-RF))  (Equation1)In this equation, the delay that is implemented in the forward path(signals from the host) is the requested delay reduced by three factors;the signal path delay received over the delay management channel(Delay_(signal-path)), the intrinsic processing delay of the serial todigital conversion (Delay_(intrinsic-SD)) of the transport interface 107and the intrinsic delay in the RF to digital conversion(Delay_(Forward-RF)) of the RF to digital interface 109.DELAY_(REV)=(Delay_(Requested))−(Delay_(signal-path))−(Delay_(Intrinsic-SD))−(Delay_(Reverse-RF))  (Equation2)In this equation, the delay that is implemented in the reverse path(signals to the host) is the requested delay reduced by three factors;the signal path delay received over the delay management channel(Delay_(signal-path)) the intrinsic processing delay of the serial todigital conversion (Delay_(Intrinsic-SD)) of the transport interface 107and the intrinsic delay in the RF to digital conversion(Delay_(Reverse-RF)) of the RF to digital interface 109.

With respect to Equations 1 and 2 above, each of the delays that aresubtracted from the Requested Delay is available at the time of therequest. Moreover, any request to set a delay that results in a valuethat is less than zero or greater than DELAY_(MAX) results in anon-operative command.

The data in a communications channel frame (such as the data frame 302)includes framing information, data integrity information (e.g., at leastone of forward error correction and cyclical redundancy checking), andthe payload data. The addition of the delay monitor channel 304 and thedelay management channel 306 allows the network 100 to automaticallysynchronize message delivery and propagate end-to-end signal pathtimings for the antenna ports 110. The delay management methodsdiscussed here provides the host node 102 and each of the remote nodes104 ₁ to 104 ₁₀ with a total signal path delay within the network 100.Moreover, these methods allow each of the remote nodes 104 ₁ to 104 ₁₀to independently adjust the transport delay value to maintain a commontiming base throughout the network 100.

FIG. 4 is a flow diagram illustrating a method 400 for managingtransport delays in a distributed communications network (e.g., thenetwork 100). For example, the method 400 addresses managing thetransport delay between remote nodes and a host node in apoint-to-multipoint communications network similar to that of thenetwork 100. Advantageously, the network 100 uses the transport delaymanagement described in FIG. 4 to continuously monitor and automaticallyadjust the signal path delays for the plurality of nodes and achieve thecommon time base discussed above with respect to FIG. 3.

At block 402, the network 100 discovers individual transport delays forany adjacent nodes in the network 100. In one implementation, the hostnode and each of the remote nodes record the individual transport delaysbetween their respective adjacent nodes. At block 404, the network 100generates a signal path delay value based on the transport delaysdiscovered in block 402. In one implementation, the host node and eachlevel of the remote nodes account for internal processing delays (e.g.,processing delays for transport interfaces in the network 100) incalculating the signal path delay. At block 406, the network 100propagates the signal path delay value to each of the adjacent nodes ina first (next) level. At block 408, the signal path delay value ismodified at each of the adjacent nodes for the first (next) level ofadjacent nodes, if any are available (block 410) and continues topropagate the modified signal path delay value until the each level ofthe adjacent nodes in the network 100 has a signal path delay value. Thesignal path delay management illustrated in FIG. 4 asynchronouslyadjusts the signal path delay value to achieve the common time basebetween each of the antenna ports of the network 100.

While the embodiments disclosed have been described in the context of adistributed communications network, apparatus embodying these techniquesare capable of being distributed in the form of a machine-readablemedium, or storage medium, of instructions and a variety of programproducts that apply equally regardless of the particular type of signalbearing media actually used to carry out the distribution. Examples ofmachine-readable media, or storage media, include recordable-type media,such as a portable memory device; a hard disk drive (HDD); arandom-access memory (RAM); a read-only memory (ROM); transmission-typemedia, such as digital and analog communications links; and wired orwireless communications links using transmission forms, such as radiofrequency and light wave transmissions. The variety of program productsmay take the form of coded formats that are decoded for actual use in aparticular distributed communications network by a combination ofdigital electronic circuitry and software residing in a programmableprocessor (e.g., a special-purpose processor or a general-purposeprocessor in a computer).

At least one embodiment disclosed herein can be implemented bycomputer-executable instructions, such as program product modules, whichare executed by the programmable processor. Generally, the programproduct modules include routines, programs, objects, data components,data structures, and algorithms that perform particular tasks orimplement particular abstract data types. The computer-executableinstructions, the associated data structures, and the program productmodules represent examples of executing the embodiments disclosed.

This description has been presented for purposes of illustration, and isnot intended to be exhaustive or limited to the embodiments disclosed.Variations and modifications may occur, which fall within the scope ofthe following claims.

What is claimed is:
 1. A method for programming the delay for a node ina communication system, the method comprising: receiving a selecteddelay value for the node, wherein the selected delay value identifies adesired end-to-end transport delay between the node and a host node inthe communication system; receiving a signal path delay value at thenode, wherein the signal path delay value identifies a delay for signalscommunicated between the node and the host node, the signal path delayvalue comprising an aggregation of at least one transport delaycalculated by at least one node for at least one segment of thecommunication system between the node and the host node, wherein eachtransport delay of the at least one transport delay identifies traveltime between two adjacent nodes in the communication system; andcalculating an additional delay necessary to meet the selected delayvalue based on the signal path delay value and the selected delay value,wherein calculating the additional delay comprises subtracting thesignal path delay from the selected delay value.
 2. The method of claim1, wherein calculating the additional delay comprises calculatingforward and reverse path delays.
 3. The method of claim 1, whereincalculating the additional delay comprises subtracting the signal pathdelay value and an intrinsic delay for the node from the selected delay.4. A program product comprising program instructions, embodied on anon-transitory storage medium, the program instructions cause at leastone programmable processor in a node within a distributed communicationsnetwork having a host node to: discover a transport delay between thenode and a first adjacent node within the network, wherein the firstadjacent node is adjacent to the node within the distributedcommunication network; receive a first signal path delay value for thefirst adjacent node when the first adjacent node is not the host node,wherein the first signal path delay value identifies a delay for signalscommunicated between the first adjacent node and the host node, whereinthe first signal path delay value for the first adjacent node includesan intrinsic delay value for the first adjacent node; calculate a secondsignal path delay value for the node based on the received first signalpath delay value and the discovered transport delay when the firstadjacent node is not the host node; propagate a signal based on thesecond signal path delay value to a second adjacent node when the firstadjacent node is not the host node, wherein the second adjacent node isadjacent to the node within the distributed communication network;wherein the node is positioned in a communication path between the firstadjacent node and the second adjacent node within the distributedcommunication network; wherein the node communicates with the host nodethrough the first adjacent node within the distributed communicationnetwork when the first adjacent node is not the host node; and whereinthe node communicates directly with the host node within the distributedcommunication network when the first adjacent node is the host node. 5.The program product of claim 4, wherein the program instructions causethe at least one programmable processor in the node to discover thetransport delay between the node and the first adjacent node within thenetwork by causing the at least one programmable processor in the nodeto: determine a round trip delay between the node and the first adjacentnode; and divide the round trip delay in half.
 6. The program product ofclaim 4, wherein the program instructions cause the at least oneprogrammable processor in the node to discover the transport delaybetween the node and the first adjacent node within the network bycausing the at least one programmable processor in the node to: receivea turn-around delay for the first adjacent node; determine a round tripdelay between the node and the first adjacent node; subtract theturn-around delay from the round trip delay to produce a corrected roundtrip delay; and divide the corrected round trip delay by two.
 7. Theprogram product of claim 4, wherein the program instructions cause theat least one programmable processor in the node to discover thetransport delay between the node and the first adjacent node within thenetwork by causing the at least one programmable processor in the nodeto: set a turn-around delay for the first adjacent node; determine around trip delay between the node and the first adjacent node; subtractthe turn-around delay from the round trip delay to produce a correctedround trip delay; and divide the corrected round trip delay by two. 8.The program product of claim 4, wherein the program instructions causethe at least one programmable processor in the node to receive a firstsignal path delay value for the adjacent node using a delay managementchannel established between the node and the first adjacent node.
 9. Theprogram product of claim 4, wherein the program instructions furthercause the at least one programmable processor in the node to: receive aselected delay value for the node that identifies a desired end-to-endtransport delay between the node and a host node within the distributedcommunications network; calculate an additional delay necessary to meetthe selected delay value based on the first signal path delay value andthe selected delay value.
 10. The program product of claim 9, whereinthe program instructions cause the at least one programmable processorin the node to calculate the additional delay necessary to meet theselected delay value by causing the at least one programmable processorin the node to: subtract the first signal path delay value from theselected delay value.
 11. The program product of claim 9, wherein theprogram instructions cause the at least one programmable processor inthe node to calculate the additional delay necessary to meet theselected delay value by causing the at least one programmable processorin the node to: calculate a forward path delay; and calculate a reversepath delay.
 12. The program product of claim 9, wherein the programinstructions cause the at least one programmable processor in the nodeto calculate the additional delay necessary to meet the selected delayvalue by causing the at least one programmable processor in the node to:subtract the signal path delay value and an intrinsic delay for the nodefrom the selected delay value.
 13. A remote node in a communicationsnetwork having a host node, the remote node comprising: a remote nodeprocessor operable to execute program instructions that cause the remotenode processor to: calculate an additional delay necessary to meet aselected delay value based on a signal path delay value by subtractingthe signal path delay value from the selected delay value; wherein theselected delay value is received at the remote node, wherein theselected delay value identifies a desired end-to-end transport delaybetween the remote node and the host node; and wherein the signal pathdelay value is received at the remote node, wherein the signal pathdelay value identifies a delay for signals communicated between theremote node and the host node, wherein the signal path delay valueincludes an aggregation of at least one transport delay calculated by atleast one node for at least one segment of the communication systembetween the remote node and the host node, wherein each transport delayof the at least one transport delay identifies travel time between twoadjacent nodes in the communication system.
 14. The remote node of claim13, wherein the remote node processor calculates the additional delaynecessary to meet the selected delay value by calculating both a forwardpath delay value and a reverse path delay value.
 15. The remote node ofclaim 13, wherein the remote node processor calculates the additionaldelay necessary to meet the selected delay value by subtracting thesignal path delay value and an intrinsic delay for the remote node fromthe selected delay value.